This giant bacterium lives up to its name

The swamp-dwelling species is large enough to see without a microscope

The newly discovered bacterium Thiomargarita magnifica, can be seen with the unaided eye. The slender, white creatures (several shown here) measure 1 to 2 centimeters (0.4 to 0.8 inch) long.

Tomas Tyml

A swamp-dwelling microbe is shaking up the scientific world. This record-breaking bacterium is so big you can spy it without a microscope.

The newly discovered species is around one centimeter (0.4 inch) long. Its cells also turn out to be surprisingly complex. Scientists named the new microbe Thiomargarita magnifica (Thee-oh-mar-guh-REE-ta Man-YIH-fih-kah). They described its discovery in the June 23 issue of Science.

The giant bacterium looks a bit like a human eyelash, says marine biologist Jean-Marie Volland. He works at the Laboratory for Research in Complex Systems. It’s in Menlo Park, Calif. The newfound microbe is about 50 times the size of other known giant bacteria. It’s some 5,000 times larger than average bacterium. The longest specimen of the new species measured roughly 2 centimeters.

The genetic material in most bacteria float freely inside their cells. But T. magnifica’s DNA is coiled in a membrane-walled sac. Such a compartment is typical of the more complex cells found in eukaryotes. That’s the group of organisms that includes plants and animals.

Olivier Gros first discovered the new bacteria in a mangrove swamp in the Caribbean’s Lesser Antilles. A marine biologist, Gros works at the Université des Antilles Pointe-á-Pitre in Guadeloupe, France. At first, he thought the slender, white creatures could not be bacteria — they were just too big. But genetic studies showed he was wrong. Additional studies would reveal those DNA-holding sacs in their cells.

Scientists had long thought that bacteria’s lack of cellular complexity limited how large they could grow. But T. magnifica is “breaking our way of thinking about bacteria,” says Ferran Garcia-Pichel, who was not part of the study. He’s a microbiologist at Arizona State University in Tempe. People think of bacteria as small and simple. But that view could have researchers missing lots of bacterial species, he says. It’s like scientists thinking the biggest animal that exists is a mouse, but then someone discovers the elephant.

What role T. magnifica plays among the mangroves is still unknown. Scientists are also uncertain as to why the species evolved to be so big. It’s possible that being long helps the cells gain access to oxygen and sulfide, says Volland. The bacteria need both to survive.

Erin I. Garcia de Jesús is a staff writer at Science News. She holds a Ph.D. in microbiology from the University of Washington and a master’s in science communication from the University of California, Santa Cruz.

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